The Cook County Medical Examiner said an autopsy performed Friday was inconclusive as to why Thornwood High School security guard Richard Cowser, 54, died while trying to break up a school fight.

Cowser fell into a school locker on Thursday afternoon and died at a local hospital. Police are questioning two students, both females, who were involved in the fight and reviewing school security cameras. Student Tyshon Boyd gave ABC7 cell phone video of the fight.

Police say the teenaged girls were arguing over a pair of designer jeans when Cowser tried to break up the fight. It isn't clear if he was actually struck by a student or if he just fell, hitting his head on the locker.

Boyd said Cowser's face turned purple when he hit the ground. "The security guards run over there, trying to break the fight up. He jumped in front of the girls and he just slowly passed out. He leaned over into the locker and passed out," Boyd said.

Cowser is from the South Holland area. He and his wife moved back recently from Florida.

"Just fresh air in this area because it's nice and quiet here. A blessing to add to the cul de sac, to the community, itself. Good people," Acie Cheairs, neighbor, said.

Cowser's family said they believe the body builder, who students say resembled "Hulk" was in good shape.

Flags at Thornwood High School were being flown at half-mast on Friday afternoon.